Photographic emulsion



July 25, '1939` B. H. CARROLL 2,166,938

APvxomocnumc EMULSIQN Filed March 29, 1937 l MIXTUPE 40 44 l 48 52 56 60640mb g/vzaxar/f/acwfdacm/v//vf 4s 52 5b @o mom# @o wmp,

BluILC'alfrolh y INVENTOR: 777710 BY @wea f 6o wmp Patented July- 25,1939 PATENT OFFICE PHOTOGRAPHIC EMULSION Burt H. Carroll, Rochester, N.Y., assigner to Eastman Kodak Company, Rochester, N.`Y., a corporationof New Jersey Application March 29, 1937, Serial No.` 133,589

13v Claims.

This invention relates to sensitized photographic emulsionsand moreparticularly to photographic emulsions, such as those of thegelatinosilver-halide type, containing a mixture or combination of twolor more sensitizing materials, at least one of which cooperates with atleast one other to alter thesensitivity of the emulsion to a greaterdegree than is possible with any one of the sensitzing materials alone.The sensitization .produced by my combinations is always greater, insome spectral region, than the sum total of the sensitizations producedby the separate sensitizing materials. The sensitizing materials of mycombinations are substances generally referred to as dyes and moreparticularly as dyes of the cyanine class.

It is known in the art of making photographic emulsions that'certaindyes of the cyanine class alter the sensitivity of photographic4emulsions of the gelatino-silver-halide type, when incorporated therein.The sensitizing eiect produced by the dyes does not increaseproportionally to the amount of dye, but passes through a maximum as theconcentration is increased. lWithin the range of concentration mostuseful inv practice, the sensitivity increases much more slowly than theconcentration of the dye. bined effect of two or more dyes on anemulsion is rarely equivalent to the sum of their separate effects, ingeneral it is much less. Most commonly, the combined` effect is nogreater than the effect. of a single one of the dyes employed in aconcentration equalv to the s um of the concentrations of all the dyesin the combination.

. Very frequently, the combined effect of two dyes is less than that ofone of them alone.

I have found with certain mixtures or combinations of two or morecyanine dyes, that the sensitization is substantially greater, in somespectral region, than that of any one of the dyes in the absence of theother or others. I will call this phenomenon supersensitization. Ingeneral, at least one dye ofmy combination may be said y to besupersensitized by the other or others. 'I'he dye which issupersensitized may be called the Likewise, the com-l sensitizationproduced by dye A increases in the presence of dye B which sensitizesonly for the green. When two or more dyes sensitize for ap#- proximatelythe same or widely overlapping spec,- tral regions (as in a number ofthe cases to be described in the instant application),supersensitization `can still be detected, because if super-lsensitization obtains in such cases, the total opi tical sensitizationproduced by a combination of two or more dyes will always be greater,underlo favorable conditions, than that which' can be produced by anydye of the combination alone at any concentration The magnitude ofsupersensitization depends upon the relative and absolute concentrationsof the dyes in the emulsion and 15 on the type of emulsion. In theinstant application, the supersensitizing effects have been clearlydemonstrated under suitable conditions which are applicable tocommercial practice.

This application deals with emulsions containing supersensitizingmixtures or combinations of one or more 8-alkyl -unsymmetricalcarbocyanine dyes, in which one of the heterocyclic nuclei is anarylo-oxazole nucleus, such as vbenzoxazole or naphthoxazole, forexample, and the other heterocyclc nucleus is an arylothiazole oraryloselenazole nucleus, such as benzothiazole, benzoselenazole andnaphthothiazole, for example, together with one or more pseudocyaninedyes. Just how the dyes of my mixtures cooperate to give a super- 30sensitizing effect is not known. I shall refer to the mixtures ascombinations, although I do not intend to imply that the. dyes arechemically Y combined.

An object of my invention, therefore, is to provide photographicemulsions containing a supersensitizing combinaticn of cyanine dyes. Afurther object is to provide a process -for sensitlzing photographicemulsions with supersensitizing combinations of dyes and to provide amethod of 40 increasing the yellow and green sensitivity of emulsionssensitized tothe yellow and -green regions of the spectrum. A still`further object is to provide a photographic element comprising asupport coated with such supersensitized emulsions. Other more specificobjects lwill become apparent hereinafter. e

The dyes which I employ in my supersensitizing combinations are"sensitizers of photographic emulsions when used therein alone. Whilethere is more than-one manner of formulating and naming the dyes which Iemploy in practicing ny invention, it is believed that the formulas,systems of nomenclature and names used herein are in accordance withthose used during the Among the -alkyl unsymmetrical carbocyanine dyesuseful in practicing my invention are the following:

The 8-alkyloxathiacarbocyanines, which can be represented by thefollowing general formula:

The 8-alkyloxaselenacarbocyanines, which' can vbe represented by thefollowing general formula:

The 8-alkyl 3,4 benzoxathiacarbocyanines. which can be represented bythe following general formula:

i R X The 8 alkyl-3,4-benzoxaselenacarbocyanines,

which can be represented bythe following general formula:

The 8-alkyl `3',4' benzoxathiaoarbocyanine, which can be represented bythe following general formula: 7^

In all ofthe above formula, A, R and Rf represent alkyl groups and Xrepresents an acid medusa radical. I have found it convenient to employthe carbocyanine dyeiodides (where X represents iodine) inpracticlng myinvention. However, other dye-salts, such as the chlorides, bromides,perchlorates, a1kyl -sulfates, alkyl-p-toluenesulfonates can beemployed, for example. I have found it advantageous to employ dyeswherein A' represents methyl or ethyland R and R' represent an alkylgroupvof one-'to four carhydroxyethyl, lsobutyl or the like, inpracticing my invention. More' specifically I have found thedyes whereinA represents methyl or ethyl and R and R' represent ethyl to beespecially useful. The nuclei of the dyes can carry simple substituentswhich do not interfere with sensl tizing properties, such as, forexample, alkyl, alkoxy, chloro or amino groups.

These 8-alky1 unsymmetrical carbocyanine dyes can'be prepared accordingto the method described `in the copending application of Leslie G. S.Brooker and Frank L. White. Serial No. 30,736, filed July 10, 1935. Themethod of Brooker and White comprises reacting. in the presence of awater-binding agent, e. g, acetic anhydride, a 1-methylbenzoxazoleorg-methylnaphthoxazole `Quaternary salt with an `acylmethylenederivative of the following formula:

wherein A and R. represent alkyl groups, D represents a phenylene or anaphthylene group and 5 4 4 5' s s' e' o 2' 7 12 :CH- 1, 1' s N/ EIR s'a R x The thia-2oyanine dyes which can be represented by the followinggeneral formula:

The selena-2cyanine dyes which can be represented by the followinggeneral formula:

The oxazolo-z'l-cyanine dyes which can be represented by the followinggeneral formula:

o Hcs/1\ s (alkyl) (phe y1) P14 20:01;-

i The benzothia-2'cyanine dyesl which can be A represented by thefollowing general formula:

example, as the chlorides, bromides, perchlorates,

alkylsulfates or alkyl-ptoliienesulfonates. I have found it advantageousto employ pseudocyanine dyes wherein R and R represent an alkyl group ofone to four carbon atoms, such as methyl,

isobutyl, ethyl, nibutyl, allyl or -hydroxyethyl, for example. The dyeswherein R and R.' represent ethyl are particularly useful in practicingmy invention. The pseudocyanlne dyes can be substituted in their nucleiwith simple substituents which vdo not interfere with sensitizingproperties, such for example, as alkyl, chloro, alkoxy or amino groups.

Brooker and Keyes in the Journal of the Ameri*- can chemicai society,v01. 57, pages 2488-2491 (1935) have reviewed the literature pertainingto vpseudoeyanine dyes sindA describe methods for the iso ,other saltswhich may be light-sensitive.

way of illustration, the herein described superpreparation thereof.Oxazolo-2cyanine dyes are described in U. S. Patent No. 1,969,446.

The objects of my invention can be accomplished by merely incorporatingone or more sensitizing 8-lalky1 unsymmetrical carbocyanine dyestogether with one or more sensitizing pseudocyanlne dyes capable ofsupersensitizing the -alkyl-A carbocyanine dye in a photographicemulsion. My invention isparticularly directed to the ordinarilyemployed gelatina-silver-halide emulsions. However, my supersensitizingcombinations can be employed in emulsions in which the carrier `is otherthan gelatin, for example, a resinous substance or cellulosic derivativewhich has substantially no deleterious effect on the light-sensitivematerials. As' silver halide emulsions, I include such emulsions as arecommonly employed in the art, for example, silver chloride or silverbromide emulsions which can contain By sensitized emulsions wereprepared employing an ordinary gelatino-silver-bromide emulsion ofordinary concentration (approximately 40 g. of silver halide, perliter). The dyes were generally employed in concentrations in the orderof 10 mg.

each, per. liter of ordinary emulsion, but can be The methods ofincorporating dyes in-'emul- 'l sions are simple and well known to thoseskilled in the art. In practicing my invention, the dyes of mycombinations can be added separately or together. It is convenient toadd dyes separately in the form of their solutions in appropriatesolvents. The solvent must, of course, be' compatible with the emulsion,substantially free from any deleterious effect on the light-sensitivematerials and capable of' dissolving the dyes. Methanol has provensatisfactory as a solvent for the dyes in practicing my invention. Thedyes are ad.-

vantageously incorporated in the finished, washed emulsion anu should beuniformly distributed throughout the emulsion. The emulsion can then beconverted into a photographic element by' lcoating upon a support, suchas glass, cellulose acetate, cellulose nitrate, other cellulose deriva.tive or resin. in a manner well-known in the art. The followingcombinations or mixtures of dyes are illustrative of my invention. Theseillustrations are not intended to be limiting:

. 8-alkyl t1min/'mmetrical. Pswdocyanine yWhile I have illustrated onlycombinations containing one 8-alkyl unsymmetrical carbocyanine andonepseudocyanlne, my combinations can as well contain one 8-alky1unsymmetrlcal carbocyanine cooperating with two pseudocya# nlnes to givea supersensitizing effect. Likewise. my combinations can contain twopseudocyanines cooperating with onel 8alkyl unsymmetrical carbocyanine.

8-alkyl unsymmetrical carbocyanine or pseudocyanine dyes containing the5,6-benzothla nucleus are almost generally of lesser utility inpracticing my invention.- Combinations containing such dyes ordinarilyshow smaller. and in many cases much smaller supersensitizing effects.Among the oxazolo2'cyanines, those lsubstituted vin the 4position of theoxazole nucleus by an alkyl group, such as methyl, or byA anr aryl groupof the benzene series, such as` In general, it can be said of mycombinations that the 8-alkyl unsymmetrical carbocyanine is the dyesupersensitized (basic-sensitizer) and the pseudocyanlne is thesupersensitizer. However, the nature of this relationship between thedyes of my combinations is frequently difilcult to determine and is, infact, immaterial to the practice of my invention. V

The accompanying drawing is by way of illustrations and depicts thesupersensitizing effect of four of `my new combinations. Each figure ofthe drawing is a diagrammatic reproduction of three spectrogramsshowing, first, the sensitivityof -a silver bromide emulsion containingan "8alkyl unsymmetrical carbocyanine dye (represented by thedot-and-dash line in each figure),-

second, the sensitivity of the same silver bromide emulsion containing.i aV pseudocyanlne dye (represented by thedotted line` in e'ach figure)`l mg. per liter of emulsion, and curve C repre-I sents the sameemulsioncontainlng 2,2'diethy1 8methyl-3,4benzothiacarbocyanine iodideand 3,1'-diethyl-4-phenyloxazolo-'2'-cyanine iodide in concentrations of10 and 20 mg. per liter of emulslonfrespectively. `The sensitivity ofthe emulsion representedA by curve C, measured throughv a Wratten 12illter is 60% greater than that of the emulsion represented by curve A.

In Fig. 2, curve D represents the sensitivity of an ordinary silverbromide emulsion containing nine iodide in a concentration of about 10mg. per liter; curve Ev represents the same emulsion containing2,1'-diethylthia-2'cyanine iodide in a concentration of about mg. perliter, and curve F represents the sensitivity of the same emulsionlcontaining 2,2-dimethyl8ethyl3,4'-benzoxathiacarbocyanine iodide and2,1dlethylthia2- cyanine iodide in concentrations ofv about 10 and 20mg. per liter, respectively. 'Ihe sensitivity of the emulsionrepresented by curve F, measuredv through a Wratten (A) iilter is 100%greater than that of the emulsion represented by curve D.

InFlg. 3,- curve G represents the sensitivity of an ordinary silverbromide emulsion containing 2,2'-diethyl-8-methyl-oxathiacarbocyanineiodide in la` concentration of' about 10 mg. per4 liter;curvev'Hrepresents the sensitivity of the same emulsion containing2,1diethyl4cliloro thia2cyanine iodide in a concentration of about 10mg. per liter, and curve I represents the` sensitivity-of the sameemulsion containing 2,2-diethyl-8-methyloxathiacarbocyanlne iodide- Aand2,1'-diethyl-4-chlorothia-2'-cyanine iodide each vin a concentrationofabout 10 mg. per liter.

In Fig. 4. curve J represents the sensitivity of an ordinary silverbromide emulsion containing 2,2,-trlethyloxaselenacarbocyanine ,iodidein a concentration of about 10 mg. per liter; curve K represents thesensitivity of the sa'me emulsion containing2,1'-diethyl-i-chlorothia-Z'-cyanine iodide in a concentration oi about10 mg. per

liter, and curve L represents the same emulsion' containing2.,'2',-8triethyloxaselenacarbocyanine iodide and2,1'-diethyl-4-chlorothia-2'-cyanine iodide each in 4a concentration ofabout 10 mg. per liter. a

'I 'he spectrograms corresponding to the ilgures oi' the accompanyingdrawingwere made in a I. grating spectrograph with an optical wedgehaving an optical density gradient of 1.0 for each Lhorizontal line inthe spectrogram. Where the spectrograms were compared as in each of theilgures of the drawing, the exposures were for the same time and testplates of each group were developed together. f

Still further examples showing the application of my invention could becited, but the foregoing `will be sumcient to teach thoseskilled in theart the manner in'whicli my invention is carried out and the principlesof sensitizing photographic emulsions with supersensitizlng combinationssuch as described herein.

Cyanlne dyes containing hydroxyalkyl groups can be prepared from,cyclammonium quaternaryr salts prepared by reacting heterocyclicnitrogen bases with halohydrins, e. g. ethylene halohydrins andpropylene halohydrins. It is advantageous to employ the bromohydrins.Ihe heterocyclic nitrogen base and the bromohydrin are merely heatedtogether for several hours, e. vg. 25 to 30 hours or longer, at about100 C., though 150 C. can be employed. An excess of the bromohydrin isadvantageously employed. Following the reaction, the solid reactionproduct is advantageously converted to the iodide by treatment withpotassium iodide. This can be accomplished by dissolving the c'rudeQuaternary bromide in hot water and treating the solution with a hotaqueous solution of potassium iodide (1 g. per cc. of water). Cyaninedyes con'taining hydroxyalkyl groups are-described inthe application ofLeslie G. S. Brooker and Lloyd A. Smith, Serial No. 133,524, filed ofeven date'herewith.

The arylo-oxazole nuclei, such as benzoxazole and naphthoxazole nucleifor example, are niore properly referred to as aroxazole nuclei.Likewise the arylothiazole and aryloselenazole nuclei, such asVbenzothlazole, benzoselenazole and naphthothiazole nuclei for example,are more properly referred to as arothiazole and aroselenf azole nuclei.-In these aroxazole, arothiazole and aroselenazole nuclei, the positionadjacent to the 4 azole nitrogen atom is known as the alpha position.vThus, in the case of the aroxazole nucleus, benzoxazole, the alphaposition is as shown in the following formula:

Let-

"dyes, v8-allryl--3,dbenzoxathiacarbocyanine dyes.

8-alkyl-3,4-benzoxaselenacarbocyanine dyes, 8-alkyl-3',4'benzoxathiacarbocyanin dyes and 8-Ialkyl-3,43',4*-dibenzoxathlacarbocyanine dyes.

3. A photographic gelatlno-silver-halide emulsion containing asupersensitizing combination, one sensitizing pseudocyanine dye selectedfrom the group consisting of 2,2'cyanine dyes, thia- 2cyanine dyes,selena-2'cyanine dyes, 4phen ylcxazolo2cyanine dyes and3,4-benzothia-2'- `cyanine dyes, with at least one sensitizingcarbocyanine dye selected from the group consisting, of-alkyloxathiacarbocyanine dyes, 8-allryloxaselenacarbocyanine dyes,8alky1-3,4benzoJ;a-`

4. A photographic gelatine-silver-halide emul-` sion containing asupersensitizing combination of at least one sensitizing8-alky1-3,4benzoxa thiacarbocyanine dye with at least one sensitizingpseudocyanine dye.

5. A photographic gelatino-silver-ha'lide emulsion containing asupersensitizing combination thiacarbocyanine dye with atleast onesensitizing pseudocyanine dye.

6. A photographic gelatino-silver-halide emul- .sion containing asupersensitizing combination of at least one sensitizing8-alkyl3,4,3,4'di

benzoxathiacarbocyanine dye with at least one sensitizing pseudocyaninedye.

7. A photographic gelatina-silver-halide emulsion containing asupersensitizing combination 3,4benzoxathiacarbocyanne halide in' whicheach of the 2- and 2'alkyl groups contains from one to four carbonatoms, with at least one sensitizing3,1-dialkyl-4-phenyloxazolo-2"cyanine halide in which each of the -3-and 1"-a1kyl groups contains from one to four carbon atoms.

8. A photographic gelatinorsilver-halide emulsion containing asupersensitizing combination 3',4"benzoxathiacarbocyanine halideA inwhich each of the 2- and 2'-alkyl groups contains from one to fourcarbon atoms, with at least one sensitizing 2,1dialkylthia-2"cyaninehalide in Iwhich each of the 2- and 1alkyl groups contains from one tofour carbonl atoms` 'Q 9. A photographic gelatino-silver-halide emulninedye in which each of the alkyl groups con-v tains fromone to for carbonatoms, with 'at least one sensitizing carbocyanine dye selected from thegroup consisting of 2,2'dialkyl-il-alkylalcance oxathiacarbocyaninedyes, 2,2'dialkyl8a1kyl oxaselenacarbocyanine dyes, 2,2diakyl8alkyl3,4-benzoxathiacarbocyanine dyes, 2,2'dialkyl8-alkyl-3,4-benzoxaselenacarbocyanine dyes, 2,2'- dlalkyl .8 alkyl3',4'benzoxathiacarbocyanine dyes and2,2'dialky1-8alkyl-3.4,3',4dibenzcxa thiacarbocyanine dyes in which eachof the 8- alkyl groups is an alkyl group selected from the groupconsisting of methyl and ethyl and each of the Z- alkyl and 2alkylgroups contains ,from one to four carbon atoms.

11. A photographic gelatino-silver-halide emulsion containing asupersensitizing combination o f at least one sensitizing1,1'idialkyl-2,2'cya -nine dye in which each of the'alkyl groupscontains from one to four carbon atoms, with at least one sensitizingcarbocyanine dye selected from thegroup consisting of2,2'dialkyl8alkyloxa thiacarbocyanine dyes, 2,2'-dialkyl-8-alkylom.-Vselenacarbocyanlne dyes, 2,2'dialkyl8alkyl 3,4-benzoxathiacarbocyaninedyes, 2,2dialky1 8-alky1-3,fi-benzoxaselenacarbocyanine dyes, 2,2'-

thiacarbocyanine dyes in which each of the 8- alkyl' groups is an alkylgroup selected from the' group consisting of methyl and ethyl and eachof the 2-alk"yl and 2alkyl groups contains from one to four carbonatoms.

12. A photographic gelatino-silver-halide emulsion containing asupersensitizing combination of at least one sensitizing3,1'dialkyl4phenyl oxazolo-2'cyanine dye in which each of the alkylgroups contains from one to four carbon atoms,with at least onesensitizing carbocyanine 35 dye selected from the Kgroup consisting o!v2,2'-

each of the 8-alkyl groups is an alkyl group selected from the groupconsisting of methyl and ethyl and each of the 2-alkyl and 2alkyl groupscondtains from one to four carbon atoms.

13. A photographic gelatino-silver-halide emulsion containing asupersensitlzing combination of at least yone sensitizing2,2dimethy18-ethyl 3,4benzoxathiacarbocyanine dye ,with at least onesensitizing 2 ,1diethylthia2'cyanine dye. -l

Y BURT H. CARROLL.

